The invention relates to a vertical drilling boom for a rock drilling equipment comprising a vertical boom mounted at its lower end turnably about a horizontal shaft with respect to a carrier of the rock drilling equipment, the vertical boom comprising two boom portions mounted longitudinally slideably with respect to each other and an actuating device for displacing the boom portions with respect to each other to adjust the length of the boom; at least one actuating device for turning the boom about the shaft; a boom head for turning a feeding beam of a rock drilling machine mounted to the boom about a shaft transverse, preferably perpendicular, to the longitudinal axis of the boom; and means for turning the boom head.
On drilling so-called production holes parallel with each other in a rock, especially in tunnels, so as to systematically blast off material to be excavated, it is customary to use a vertical drilling boom for carrying out the drilling process. The vertical drilling boom is a vertical boom the lower end of which is mounted in the drilling equipment turnably about a horizontal axis in such a way that the upper end of the boom can be turned along a curved path with respect to the drilling equipment. At the upper end of the vertical boom there is provided a swing joint the shaft of which is parallel to the shaft of the lower end of the boom and to which the drilling boom is connected by means of a so-called Herculean joint. The Herculean joint is provided with an arm attached to the swing joint of the upper end of the boom, the other end of the arm being attached to the feeding beam of the drilling machine turnably about an axis parallel to the turning axis in such a way that when the vertical boom is tilted, the feeding beam is maintained in the same direction and in the same position in the longitudinal direction of the feeding beam with respect to the joint of the lower end of the vertical boom, and, as a result, with respect to the rock to be drilled.
The use of the Herculean joint has many disadvantages due to its complicated construction and the great number of joints. The displacement of the feeding beam from hole to hole is complicated for the operator and the displacement is very difficult to automate as the arrangement would require several sensors and adjusting devices which have to be controlled. A further disadvantage is that the solution requires several actuating devices to which a great number of pressure fluid hoses has to be drawn, whereby the provision of the required hoses is difficult to realize in such a way that all the required positions of the boom are possible. As a result, the arrangement involves large bunches of hoses and the dimension of the vertical boom in the direction of the turning axis is large so that the dimensions of the equipment will be unnecessary large.